1. Field of the Invention
The present invention relates to an insulation displacement contact and an electric connector (insulation displacement connector) using the same.
2. Description of Related Art
A connector to be attached to an insulated wire has a resin housing and a contact (terminal metal fitting) secured to the housing. An insulation displacement contact has the structure in which a slot for holding the core wire portion of an insulated wire is formed between a pair of insulation displacement blades for breaking up the insulation of the insulated wire. When such an insulation displacement contact is used, the contact and the core wire portion of the insulated wire can be electrically connected to each other merely by pushing the insulated wire into the slot of the insulation displacement contact. A connector using such an insulation displacement contact is called an insulation displacement connector.
For example, as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 59-42785 (1984), the insulation displacement contact has the arrangement in which a pair of insulation displacement blades forming a slot as mentioned above are connected at their bases to each other and that the insulation displacement blades are provided at the outer sides thereof with a pair of contact pieces for connection with the contact of a base connector (board-side connector). Each of this pair of contact pieces is made of a uniform-width plate-like body which extends beyond the base of each insulation displacement blade up to the side opposite to the inlet of the slot. Each plate-like body is provided at the tip thereof with a contact portion for nipping the contact of the base connector.
In the insulation displacement connector disclosed in the above-mentioned Publication, the tips of the pair of contact pieces are inwardly bent such that the contact of the base connector is held between and by the tips thus bent.
A connector used in a recent small-size device including, as a typical example, a digital still camera, a video camera, a cellular phone, a PDA (personal digital assistant) or the like, is extremely miniaturized in size, and is a multi-pole connector having a number of poles. Accordingly, the insulation displacement connector is inevitably extremely miniaturized in size; therefore, has no spatial room for providing bent portions at the tips of the contact pieces as the insulation displacement contact disclosed in the above-mentioned Publication.
On the other hand, when an insulated wire is inserted into the slot between the pair of insulation displacement blades, the slot is resiliently deformed and expanded. At this time, the pair of insulation displacement blades are rotated around their bases. Consequently, the pair of contact pieces connected to the outer sides of the pair of insulation displacement blades are also rotated to narrow the gap between the pair of contact portions. In the case of an insulation displacement connector extremely miniaturized in size, the gap between the pair of contact portions is often eliminated to cause the contact portions to come in contact with each other.
Under such circumstances, when the contact of a base connector is inserted between the pair of contact portions, the gap between these contact portions is press opened and expanded. At this time, when the contact pieces are provided at the tips thereof with bent portions as done in the above-mentioned Publication, the bent portions and the entire contact pieces are resiliently deformed, causing the base connector contact to be resiliently held or nipped by and between the contact portions.
However, for an extremely miniaturized insulation displacement contact in which the contact pieces cannot be provided at their tips with bent portions, the insertion of the base connector contact has to rely solely on the resilient deformation of the contact pieces in their entirety. However, when each of the contact pieces is made of a uniform-width plate-like body, stress is concentrated on the base of the contact piece. More specifically, as a matter of fact, the resilient deformation of the bases of the contact pieces produces, between the pair of contact portions, a gap for receiving the base connector contact.
On the other hand, in a multi-pole connector extremely miniaturized in size, the contact pieces are also extremely miniaturized in size. Accordingly, when the base connector contact is inserted between the contact portions, the amount of expansion and deformation of the contact pieces readily exceeds a resilient deformation range and enters a plastic deformation range. Under such circumferences, the contact pieces loose almost all of its restoring force. It is therefore not possible that the contact portions come in resilient contact with the base connector contact. This may possibly injure the reliability of electric connection therebetween.
For example, when the contact pieces are not connected to the outer sides of the pair of insulation displacement blades, but are connected to the bases thereof, the above-mentioned problem is somewhat relaxed. In such a case, however, the entire height of the insulation displacement contact is equal to the sum of the height of the insulation displacement blades and the height of the contact pieces. This results in increase in the entire height of the insulation displacement connector. This goes against the market demand for an electric connector to be used in a small-size electronic device.